The present invention relates to a valve housing made from steel, especially for gate valves, in which the valve housing is composed of a plurality of housing elements which are connected by welding, especially by electron beam welding. Such a valve housing includes a central housing part formed in opposite walls thereof with openings aligned along a common axis, a pair of coaxial connecting sockets, as well as connecting members connecting the connecting sockets to the central housing part and having inner annular surfaces facing a central plane of symmetry of the valve housing and forming seating faces or carrier faces for seating rings for a closer member to be mounted in the valve housing.
Various suggestions for the constructive design and the manner of assembly of such valve housings are known in the art. All these known suggestions aim in principle to correlate the different requirements for such valve housings, which, on the one hand, should satisfy the proper function and strength of the valve housing, and, on the other hand, the most simple and, therefore, inexpensive production thereof, by means of an economical compromise in an optimum manner with each other, so that the valve housing may be constructed with the smallest possible dimensions.
These conditions are valid for valve housings in which the central housing part is pressed from sheet metal and the connecting socket, for the connection of the valve housing with conduits, consist of standard tube sections, as well as for such valve housings in which the individual parts are forged in dies. These conditions are basically also independent of whether the valve housings are constructed for a plate-shaped closer member or for closer members of different configurations.
Whereas the problems resulting from the configuration of the central housing parts and their composition of separate parts can be considered as being solved in a satisfactory manner, regardless whether the various parts of the housing are pressed from sheet metal or formed by forged parts, and also independent whether the valve housing is constructed for cooperation with a closer member in form of a plate or for closer members of different configuration, an unsatisfactory solved problem for the economical production resides in a suitable weld connection between the central housing part and the connecting sockets which eventually are provided with flanges at the outer ends. This difficulty resides mainly in that any kind of used weld connection has direct influence onto the constructive design of the valve housing and inversely certain function determined characteristics of the respective valve housing influence also the position and kind of a suitable, automatically produceable welding connection. This holds true for conventional welding methods, as well as for electron beam welding lately developed and especially suitable for welding the parts of valve housings to each other.
If, for instance, the welding connection between the central hosuing part and the connecting sockets is carried out by conventional automatic arc welding, then the lead-in of the welding wire, respectively the electrode, the protecting gas and the eventually necessary welding powder is difficult at this location in which the cover flange of the central housing part and the flanges at the outer ends of the connecting sockets form between themselves a relatively small gap. It is, therefore, necessary to keep the gap so large so that the supply of wire, powder or gas, which is usually carried out through a tube, can still be provided without hinderence through the gap between the cover flange and the connecting flange. Since the flange diameters at valve housings are often standardized, the gap between cover flange and connecting flange can only be enlarged by moving the cover flange of the central housing part in direction away from the outer periphery of the flange at the outer end of the connecting socket. This will, however, result that the interior of the central housing part has to be chosen greater, especially deeper, than necessary and in the event that the central housing part is a hollow forged part it has to be made greater than necessary, respectively desirable.
Especially with central housing parts which are forged in dies, these forging dies will thus become more complicated and liable to wear. The necessary forging machines need in this case be larger and heavier than would be otherwise necessary. Especially the strokes of crank presses for die forging have to be correspondingly larger dimensioned. At the same time, the stroke of mandrels used has to be enlarged, which in turn may lead to an undesired displacement of such mandrels.
In order to facilitate the welding of the connecting sockets to the central housing part it is already known to provide the openings in the central housing part with an appropriate bead. In later developed constructions the central housing part has substantially flat side walls provided with openings into which the connecting sockets are welded. Thereby the connecting sockets form, however, relatively complicated forged parts which are provided at the inner ends with enlargements and smooth tubes can only be welded into the openings of the central housing part if they are constructed with heavier walls than would be necessary for operating reasons.
In the known constructions the welding seams between the central housing part and the connecting sockets are preferably simple annular seams similar to such annular seams which are used for the welding connection of tube sections. Only such simple annular seams may be produced automatically, especially also when electron beam welding is used. They have also the advantage that the perfect formation of the welding seam can be subsequently ascertained by X-ray examination.
These known constructions have, however, the decisive disadvantage that, in order to carry out a perfect welding, the dimensions of the housing in view of the necessary large distance between the housing flanges on the one hand, and the connecting socket flanges on the other hand, must be chosen essentially greater than would be necessary for the proper function and rigidity of such a valve housing.